BOILEE No. 59. 205 



brick work. Unnecessary air leakage into the furnace is pre- 

 vented by the use of a lire box. The ratio of heating surface 

 to grate surface is as large as that found in many efficient 

 horizontal tubular boilers. The rate of combustion is 

 moderately high, and the temperature of the escaping gases is 

 not excessive for bituminous coal. All these conditions are 

 favorable to economy, and they go hand-in-hand with the high 

 character of the evaporative result which the test gives. An 

 evaporation of 12.29 pounds of water from and at 212 per 

 pound of combustible, which was obtained in this case, is 

 seldom exceeded by any type of boiler. 



Boiler No. 59. 



Kind of boiler, Vertical tubular ( rolling: pin ) . 



Number used, ...... Two. 



Horse-power ( collective, basis 10 sq. ft. ) , Two hundred and eighty. 



Kind of coal, ...... George's Creek Cumberland. 



Age, Twelve years. 



Boiler No. 59 embraces a plant of two vertical boilers of 

 the rolling pin type, of the general form shown in elevation in 

 the cut of Boiler No. 51. They are provided with a flue 

 heater, the location of which, with reference to the boilers, is 

 shown in ground plan in the following cut. The heater con- 

 sists of vertical cast-iron pipes, similar to that of Boiler No. 

 33, the exposed surface of which has nearly as large an area 

 as that of the total water heating surface of the boilers. 

 Dimensions of Boiler No. 59. 



Diameter of main shell, 90 in. 



Diameter of drum and water leg, 30 in. 



Length of main shell and tubes, . . . . . 10 ft. 



Number of tubes ( collective ), 2 inches outside diameter, . 496 



Area of water-heating surface, ...... 1,880 sq. ft. 



Area of steam-heating surface, 924 sq. ft. 



Area of grate surface, . . . . . . . 90 sq. ft. 



Area through tubes 8.2 sq.ft. 



Width of air spaces and metal bars in grates, Air 1-2 in., metal 5-8 in. 



Height of chimney, 80 ft. 



Katio of water-heating surface to grate surface, . . . 20.9 to 1 

 Ratio of steam-heating surface to grate surface, . . . 10 3 to 1 



Ratio of grate surface to tube area, 11 to 1 



Area of heating surface in flue heater, 1,600 sq. ft. 



